Mars “mole” struggles to hammer its way past obstacles

A probe inside the German Aerospace Center’s Heat and Physical Properties Package, or HP3 (lower right), is attempting to hammer its way below the surface of Mars. This image also shows the InSight lander’s robot arm, used to lower HP3 to the surface. Image: NASA/JPL-Caltech

A German instrument deployed by the InSight Mars lander, designed to measure the flow of heat from the red planet’s interior, is struggling to hammer its way into the soil near the spacecraft, running into a subsurface rock or gravel bed shortly after beginning its concussive descent.

The probe, known as the “mole,” was provided by the German Aerospace Center. It is designed to dig its way to a depth of 5 meters (16 feet) trailing temperature sensors on a cable leading back to the lander. After InSight’s robot arm placed the Heat and Physical Properties Package – HP3 – on the martian surface, an internal motor and spring-driven hammer-like device began pounding into the soil below the instrument’s housing on 28 February.

But the 40-centimetre-long (16-inch) probe only made it about three quarters of the way out of its housing before running into an obstacle of some sort. The probe was designed to push its way past small obstructions, but no additional progress was seen after a second round of hammering on 2 March. Data indicate the probe is now tilted at a 15-degree angle.

“The team has therefore decided to pause the hammering for about two weeks to allow the situation to be analysed more closely and jointly come up with strategies for overcoming the obstacle,” Tilman Spohn, principal investigator of the HP3 experiment, wrote on his InSight mission blog.

Data from the probe show its sensors and electronics are working as designed, able to measure how fast the heat generated by the hammering process dissipates in the martian soil as the probe cools down. Once at the planned depth, the sensors will more accurately measure the thermal conductivity of the soil to characterise the flow of heat from the interior.

InSight’s other major science instrument, an ultra-sensitive seismometer provided by the French space agency, is operating normally.

The drill at the end of the Curiosity Mars rover’s robot arm is back in action after being sidelined for more than a year by a mechanical problem. A new technique was successfully tested 20 May after months of engineering tests on Earth.

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